Pneumonia is the leading cause of death from nosocomial infections and the second most common nosocomial infection in the US. Intubation and mechanical ventilation greatly increase the risk of bacterial ventilator associated pneumonia (VAP). Patients in ICUs are particularly vulnerable because the common ICU procedures of intubation and mechanical ventilation greatly increase the risk for bacterial VAP. In addition, the supine position, frequently used by nurses in ICUs to manage problems associated with unstable hemodynamic status, further increases the risk of VAP. Although the Centers for Disease Control and Prevention recommend the use of higher backrest positions (30-45 degrees) in mechanically ventilated patients, definitive scientific studies have not yet been done to support this recommendation. In addition to the supine position, bacterial colonization of the oropharynx is also an important risk factor for VAP. Oral health status of mechanically ventilated patients may be compromised by the patient's medical condition, treatments, intensive care unit equipment, and the patient's inability to attend to his or her own oral care. Their oral cavity is colonized with potential VAP pathogens and little is known about the oral health status or local oropharyngeal immunity in mechanically ventilated patients. As a result of critical illness, it is likely that host oral defenses are compromised. Nursing interventions related to patient positioning and oral care may assist in decreasing VAP. However, prior to the development and testing of nursing interventions it is necessary to delineate the specific effect of backrest elevation and oral health status on the development of VAP. The specific aims of this study are to describe 1) the relationship of backrest elevation on the development of VAP; and 2) the relationship of oral health status on the development of ventilator associated pneumonia. The study is a non-experimental, longitudinal, descriptive design with the patient as the unit of analysis. VAP will be quantified using the Clinical Pulmonary Infection Score. Backrest elevation will be monitored using a transduced measurement system. Oral health status includes biological measurement (salivary lactoferrin and IgA) and an oral health assessment. Data will be obtained from the medical record, biological fluids (saliva and endotracheal tube aspirates) and downloaded from the bedside monitoring system over a 7 day period for each of 60 subjects and analyzed using a mixed linear model.